Email alert
RSS2004 Vol. 16, No. 05
Recommend Articles
column
Display Method:
2004,
16.
Abstract:
The orbit functions for HLS storage ring have been studied using the simulation code MAD. The effects of alignment errors of the quadrupole, dipole magnets were simulated. The effects of these errors on the orbit distortion and coupling are then graphically analyzed to show the rms spread of the functions. The studies show that the most significant closed orbit distortion was caused by displacement of the quadrupole magnets, and the amplification factors are presented, while providing the opportunity of future upgrade in alignment. In addition, the coupling between the horizontal and vertical emittance is analyzed, and the main coupling is due to the orbit distortion.
The orbit functions for HLS storage ring have been studied using the simulation code MAD. The effects of alignment errors of the quadrupole, dipole magnets were simulated. The effects of these errors on the orbit distortion and coupling are then graphically analyzed to show the rms spread of the functions. The studies show that the most significant closed orbit distortion was caused by displacement of the quadrupole magnets, and the amplification factors are presented, while providing the opportunity of future upgrade in alignment. In addition, the coupling between the horizontal and vertical emittance is analyzed, and the main coupling is due to the orbit distortion.
2004,
16.
Abstract:
The new high voltage pulse generator is mainly composed of condense capacitors, hydrogen thyratron, high voltage transformer and voltage adapter. The total capacitance and charged voltage of the condense capacitors can be changed and controlled. The output pulse of the generator has an exponential waveform, and its rising time is 0.4～0.6μs. By adjusting the capacitors and its charged voltage, the pulse width varies from 1.5μs to 4.0μs, and the pulse amplitude varies from 10 kV to 200kV．
The new high voltage pulse generator is mainly composed of condense capacitors, hydrogen thyratron, high voltage transformer and voltage adapter. The total capacitance and charged voltage of the condense capacitors can be changed and controlled. The output pulse of the generator has an exponential waveform, and its rising time is 0.4～0.6μs. By adjusting the capacitors and its charged voltage, the pulse width varies from 1.5μs to 4.0μs, and the pulse amplitude varies from 10 kV to 200kV．
2004,
16.
Abstract:
A compact laser synchrotron source (LSS) at Peking University is proposed as a means of generating tunable, high brightness, ultra-short pulse of X rays. LSS is based on Compton scattering of intense lasers from relativistic electron beams. The properties of X rays generated from the LSS are discussed. Compared with other facilities, LSS is a compact and relatively inexpensive source. Two scattering examples of possible LSS configurations at Peking University are presented. The results of preliminary design show that the wave length of the backscattered X rays is from 0.052nm to 10.3nm, and the pulse duration by 90°scattering is 800 fs. The possible applications of LSS at Peking University are also discussed．
A compact laser synchrotron source (LSS) at Peking University is proposed as a means of generating tunable, high brightness, ultra-short pulse of X rays. LSS is based on Compton scattering of intense lasers from relativistic electron beams. The properties of X rays generated from the LSS are discussed. Compared with other facilities, LSS is a compact and relatively inexpensive source. Two scattering examples of possible LSS configurations at Peking University are presented. The results of preliminary design show that the wave length of the backscattered X rays is from 0.052nm to 10.3nm, and the pulse duration by 90°scattering is 800 fs. The possible applications of LSS at Peking University are also discussed．
2004,
16.
Abstract:
This paper introduces the calibration and the sensitivity of the turn-by-turn system applied and improved on storage ring of Hefei Light Source (HLS). It pressents the results of the compare and analysis of the damping time at 200MeV and 800MeV by the data measured with the system. The causation to limit beam current accumulation is found in the injection beam monitoring. This system was not only used to measure the damping rate, β oscillation and υ change, but also to research the injecting effectiveness and beam instability. In design, the log-ratio electronics circuit with working frequency 408MHz (2×RF of HLS) was chosen to characterize machine properties of the HLS storage ring. The logAratio signal processor has properties of low noise, wide bandwidth and wide dynamic range, as we
This paper introduces the calibration and the sensitivity of the turn-by-turn system applied and improved on storage ring of Hefei Light Source (HLS). It pressents the results of the compare and analysis of the damping time at 200MeV and 800MeV by the data measured with the system. The causation to limit beam current accumulation is found in the injection beam monitoring. This system was not only used to measure the damping rate, β oscillation and υ change, but also to research the injecting effectiveness and beam instability. In design, the log-ratio electronics circuit with working frequency 408MHz (2×RF of HLS) was chosen to characterize machine properties of the HLS storage ring. The logAratio signal processor has properties of low noise, wide bandwidth and wide dynamic range, as we
2004,
16.
Abstract:
In particle track system in Beijing, the signal from Multi-Wire Proportional Chamber(MWPC) is measured for obtaining the track of particle. Charge amplifier is an important component of this system. It can amplify and shape the small signal from MWPC before CIA(Charge Integrating ADC) converts it. The amplifier contains amplifying stage and shaping stage, and can convert the small signal from MWPC to large one whose width is 600ns．
In particle track system in Beijing, the signal from Multi-Wire Proportional Chamber(MWPC) is measured for obtaining the track of particle. Charge amplifier is an important component of this system. It can amplify and shape the small signal from MWPC before CIA(Charge Integrating ADC) converts it. The amplifier contains amplifying stage and shaping stage, and can convert the small signal from MWPC to large one whose width is 600ns．
2004,
16.
Abstract:
The phaseshifts induced by thermal effect and pressure difference between outersurface and innersurface of plane laser window are analysed. The phaseshifts caused by stressbirefringence are discussed in detail. Distributions of temperature increment, stress, phaseshifts, Strehlratio and depolarization are calculated．It is indicated that window deformation and refractive index changing with temperature are primary factors of phaseshifts and result from nonuniformity of temperature increment, making beam quality declining. Stressbirefringence is related with Miller indices of laser window surface, which results in depolarization and also affect beam quality.
The phaseshifts induced by thermal effect and pressure difference between outersurface and innersurface of plane laser window are analysed. The phaseshifts caused by stressbirefringence are discussed in detail. Distributions of temperature increment, stress, phaseshifts, Strehlratio and depolarization are calculated．It is indicated that window deformation and refractive index changing with temperature are primary factors of phaseshifts and result from nonuniformity of temperature increment, making beam quality declining. Stressbirefringence is related with Miller indices of laser window surface, which results in depolarization and also affect beam quality.
2004,
16.
Abstract:
Scintillation increases when laser propagates long distance near horizontally in the atmosphere, which limits the ability of conventional adaptive optical system. Numerical simulations based on wave optics computer code are given for different atmospheric conditions. For given Rytov variance, different turbulence strengths and propagating distances are considered. Various receiving and projecting apertures are also taken into account. Rytov variance and propagation Fresnel number have still effect on Strehl ratio. The expressions of Strehl ratio with Rytov variance are obtained from weak to strong scintillation. For given Rytov variance, Strehl ratio with Fresnel number is studied. Large aperture can benefit correction. The results show that Strehl ratio increases with Fresnel number incre
Scintillation increases when laser propagates long distance near horizontally in the atmosphere, which limits the ability of conventional adaptive optical system. Numerical simulations based on wave optics computer code are given for different atmospheric conditions. For given Rytov variance, different turbulence strengths and propagating distances are considered. Various receiving and projecting apertures are also taken into account. Rytov variance and propagation Fresnel number have still effect on Strehl ratio. The expressions of Strehl ratio with Rytov variance are obtained from weak to strong scintillation. For given Rytov variance, Strehl ratio with Fresnel number is studied. Large aperture can benefit correction. The results show that Strehl ratio increases with Fresnel number incre
2004,
16.
Abstract:
Using a ray-tracing code, the coupling characteristics on both elliptic probe and bullet probe are simulated and investigated for different parameter of the optical fiber. The results show that there is an optimal structure while the ratio between the long-axis and short-axis of elliptic probe is about 1.15 and 1.3, and the bullet probe has the optimal structure when it is a half ball. The elliptic probe is obviously more practical than the bullet probe in manufacturing process.
Using a ray-tracing code, the coupling characteristics on both elliptic probe and bullet probe are simulated and investigated for different parameter of the optical fiber. The results show that there is an optimal structure while the ratio between the long-axis and short-axis of elliptic probe is about 1.15 and 1.3, and the bullet probe has the optimal structure when it is a half ball. The elliptic probe is obviously more practical than the bullet probe in manufacturing process.
2004,
16.
Abstract:
In optics polishing process, the active lap can reshape the profile for fitting the surface of large aspheric optical component with different local position and rotating angle in real time. In this way, the high order residual error by traditional polishing technique can be overcome. In this paper, the working process of active lap is modeled. The deforming capability of the active lap matching a parabolic mirror, diameter 1.3m and F/2, is simulated and verified by experiment. The results show the active 1ap can reshape the quadratic curved figure, both symmetrically and dissymmetrically with high precision. The residual errors of deflection are analyzed．
In optics polishing process, the active lap can reshape the profile for fitting the surface of large aspheric optical component with different local position and rotating angle in real time. In this way, the high order residual error by traditional polishing technique can be overcome. In this paper, the working process of active lap is modeled. The deforming capability of the active lap matching a parabolic mirror, diameter 1.3m and F/2, is simulated and verified by experiment. The results show the active 1ap can reshape the quadratic curved figure, both symmetrically and dissymmetrically with high precision. The residual errors of deflection are analyzed．
2004,
16.
Abstract:
The chemical kinetics of Cl/HN3/I2 laser has been simulated and the effect of the density of Cl, HN3 and I2 on small-signal gain has been obtained and discussed. The results show that the coefficient of smallsignal gain could be 1.6×10－4,11×10－3 and 1.1×10－2cm－1 at 400K when the initial density of Cl was 1×1015, 1×1016 and 1×1017cm－3 respectively, the initial density of HN3 and I2 for an optimal coefficient of smallsignal gain should be 1～2 times and 2％～4% of the initial density of Cl respectively.
The chemical kinetics of Cl/HN3/I2 laser has been simulated and the effect of the density of Cl, HN3 and I2 on small-signal gain has been obtained and discussed. The results show that the coefficient of smallsignal gain could be 1.6×10－4,11×10－3 and 1.1×10－2cm－1 at 400K when the initial density of Cl was 1×1015, 1×1016 and 1×1017cm－3 respectively, the initial density of HN3 and I2 for an optimal coefficient of smallsignal gain should be 1～2 times and 2％～4% of the initial density of Cl respectively.
2004,
16.
Abstract:
A theoretical analysis and results of numerical calculations for the hot image formation in high power solid-state laser system are presented. According to holographic imaging theory, an approximately functional expression for the hot image intensity from opaque scatterer is derived, showing an intensity several times as much as the background light intensity. The hot image appears in a plane located downstream from the nonlinear medium at a distance equal to that from the scatterer to the medium. It is found that the hot image intensity and location are accurately predicted by theory and numerical calculations.
A theoretical analysis and results of numerical calculations for the hot image formation in high power solid-state laser system are presented. According to holographic imaging theory, an approximately functional expression for the hot image intensity from opaque scatterer is derived, showing an intensity several times as much as the background light intensity. The hot image appears in a plane located downstream from the nonlinear medium at a distance equal to that from the scatterer to the medium. It is found that the hot image intensity and location are accurately predicted by theory and numerical calculations.
2004,
16.
Abstract:
Owing to the presence of aerosol in the troposphere（below 12km）, traditional method which uses Rayleigh scattering spectrum to measure the atmosphere temperature has certain limitations. This paper uses a Fourier analysis method to proceed transmission curve produced by atmospheric backscattering spectrum through the iodine cell, considering the influence of the aerosol. This method can obtain the temperature profile of the troposphere under the condition of different height and different backscattering ratio.
Owing to the presence of aerosol in the troposphere（below 12km）, traditional method which uses Rayleigh scattering spectrum to measure the atmosphere temperature has certain limitations. This paper uses a Fourier analysis method to proceed transmission curve produced by atmospheric backscattering spectrum through the iodine cell, considering the influence of the aerosol. This method can obtain the temperature profile of the troposphere under the condition of different height and different backscattering ratio.
2004,
16.
Abstract:
With it developing widely into the mediumsmall caliber, the laser proximity fuze’s volume gets smaller and smaller, and its internal jamming becomes stronger and stronger, especially the interference of its supply. According to the model of the supply circuits and the practical circuits, the supply’s interference is analyzed. Through referencing related books and by doing tests and simulations, a multifilter is designed to resolve the internal supply interference for its smaller volume. And the better result is obtained.
With it developing widely into the mediumsmall caliber, the laser proximity fuze’s volume gets smaller and smaller, and its internal jamming becomes stronger and stronger, especially the interference of its supply. According to the model of the supply circuits and the practical circuits, the supply’s interference is analyzed. Through referencing related books and by doing tests and simulations, a multifilter is designed to resolve the internal supply interference for its smaller volume. And the better result is obtained.
2004,
16.
Abstract:
According to the requirement of the ICF experiments, the vacuum diffusion bonding of the aluminum and copper films were studied in high temperature circumstances(250℃). The microstructures of the joint and surface roughness are analyzed by means of SEM, XRD and an alpha-step device. The results show that the force among atoms, metallurgy combination and interface reaction are important to obtain the high quality joint of the aluminum and copper films.
According to the requirement of the ICF experiments, the vacuum diffusion bonding of the aluminum and copper films were studied in high temperature circumstances(250℃). The microstructures of the joint and surface roughness are analyzed by means of SEM, XRD and an alpha-step device. The results show that the force among atoms, metallurgy combination and interface reaction are important to obtain the high quality joint of the aluminum and copper films.
2004,
16.
Abstract:
This paper describes the principle of plasma chemical vapor deposition (CVD) for fabrication amorphous CH films and factors which influence the deposition rate. The results show that the substrate distance must be more than 0.5cm. But with the increasing of the substrate distance and the H2 flow (that is to say, the CH4 content reduses), the deposition rate reduses. When DC voltage is 550V, the deposition rate has a maximum value. By examining the structures and optical properties of a-CH films using atomic force microscopy(AFM) and UV-VIS spectrum, it is indicated that a-CH films grown by means of the hollow cathode discharge plasma CVD are endowed with dense structure, and low-rough surfaces. The rough degree of surface is approximately 10nm. These a-CH films are suitable to be used as I
This paper describes the principle of plasma chemical vapor deposition (CVD) for fabrication amorphous CH films and factors which influence the deposition rate. The results show that the substrate distance must be more than 0.5cm. But with the increasing of the substrate distance and the H2 flow (that is to say, the CH4 content reduses), the deposition rate reduses. When DC voltage is 550V, the deposition rate has a maximum value. By examining the structures and optical properties of a-CH films using atomic force microscopy(AFM) and UV-VIS spectrum, it is indicated that a-CH films grown by means of the hollow cathode discharge plasma CVD are endowed with dense structure, and low-rough surfaces. The rough degree of surface is approximately 10nm. These a-CH films are suitable to be used as I
2004,
16.
Abstract:
Acrylates/silica hybrid antireflective film was prepared by spin coating and UV curing technological process. The relationship between the mole ratio of acrylates and TEOS γvalue, peak transmission wave-length, reflective index of film were discussed. It is shown that the hybrid film has a wide band of transmission between 425~1 060nm when the γvalue is 2.0, when the transmission is above 98%.
Acrylates/silica hybrid antireflective film was prepared by spin coating and UV curing technological process. The relationship between the mole ratio of acrylates and TEOS γvalue, peak transmission wave-length, reflective index of film were discussed. It is shown that the hybrid film has a wide band of transmission between 425~1 060nm when the γvalue is 2.0, when the transmission is above 98%.
2004,
16.
Abstract:
The amplified spontaneous emission(ASE) effects in high power laser slab amplifier are investigated by theoretic simulations. A time-related 3D ASE model is developed with which the ASE effect in large aperture Nd:glass amplifier is investigated in detail. The effects of ASE to the stored energy efficiency and to small signal gain coefficient are got under different pump voltage, pump time, stored energy distribution and different gain-length product. The simulation results in the 4×2×3 amplifier indicate that the effect of ASE is stronger with the improved charge voltage, the loss of average stored energy is 21.0% by ASE, the loss of small signal gain coefficient is 16.62%，the uniformity of small signal gain coefficient is 7.44% over the aperture while pumping voltage is 23kV. The gain
The amplified spontaneous emission(ASE) effects in high power laser slab amplifier are investigated by theoretic simulations. A time-related 3D ASE model is developed with which the ASE effect in large aperture Nd:glass amplifier is investigated in detail. The effects of ASE to the stored energy efficiency and to small signal gain coefficient are got under different pump voltage, pump time, stored energy distribution and different gain-length product. The simulation results in the 4×2×3 amplifier indicate that the effect of ASE is stronger with the improved charge voltage, the loss of average stored energy is 21.0% by ASE, the loss of small signal gain coefficient is 16.62%，the uniformity of small signal gain coefficient is 7.44% over the aperture while pumping voltage is 23kV. The gain
2004,
16.
Abstract:
From Maxwell's equation a diffraction-integral-like solution of X-ray propagation is derived. The paper puts emphasis, theoretically and numerically, on the analysis of the effect of refractive index gradient on the beam parameters. The results show that the higher is electron density, the effect is more evident. It has a direct impact on the distribution of the beam intensity, the diffraction and the deflection of the X-ray beam.
From Maxwell's equation a diffraction-integral-like solution of X-ray propagation is derived. The paper puts emphasis, theoretically and numerically, on the analysis of the effect of refractive index gradient on the beam parameters. The results show that the higher is electron density, the effect is more evident. It has a direct impact on the distribution of the beam intensity, the diffraction and the deflection of the X-ray beam.
2004,
16.
Abstract:
As widely applied in laser lithography and laser micromachining, excimer laser should have high stability and uniformity of beam intensity profile. This paper introduces the beam profile characteristics of excimer lasers and the beam profilometry. Experimentally, beam intensity profile of a XeCl laser and an ArF laser were diagnosed and evaluated by employing a computer with beam profile analyzer. The beam uniformity were also emphatically measured and discussed.
As widely applied in laser lithography and laser micromachining, excimer laser should have high stability and uniformity of beam intensity profile. This paper introduces the beam profile characteristics of excimer lasers and the beam profilometry. Experimentally, beam intensity profile of a XeCl laser and an ArF laser were diagnosed and evaluated by employing a computer with beam profile analyzer. The beam uniformity were also emphatically measured and discussed.
2004,
16.
Abstract:
This paper reports the experimental results of the angular distribution of hot electrons during the interaction of ultrashort ultra-intense laser with solid targets. It shows that the divergence angle of hot electrons with the high energy was smaller than that of hot electrons with the low energy. There are two peaks in the angular distribution of hot electrons with the high energy: one peak in specular direction is due to several absorption or acceleration mechanism, whereas the other peak close to the normal of the target is expected by the resonance absorption and is well consistent with H. Ruhl et al's theory(1999)．
This paper reports the experimental results of the angular distribution of hot electrons during the interaction of ultrashort ultra-intense laser with solid targets. It shows that the divergence angle of hot electrons with the high energy was smaller than that of hot electrons with the low energy. There are two peaks in the angular distribution of hot electrons with the high energy: one peak in specular direction is due to several absorption or acceleration mechanism, whereas the other peak close to the normal of the target is expected by the resonance absorption and is well consistent with H. Ruhl et al's theory(1999)．
2004,
16.
Abstract:
Laser beam automatic alignment systems are used to align the SG-Ⅲ prototype facility laser. Considering the facility qequirement, combining the key technique of automatic alignment, according to the image relay of the pinhole, utilizing the optical position and the spatial location of the four pinholes of the main spatial filter in the four-pass beam in the SG-Ⅲ, this paper presents a reasonable scheme for automatic aligning in the four-pass amplifier, which has been fully checked on the multi-pass amplifier experiment system．The centering sensitivities of the system are less than 0.5% of the beam diameter. The pointing sensitivities of the system are less than 10μm.
Laser beam automatic alignment systems are used to align the SG-Ⅲ prototype facility laser. Considering the facility qequirement, combining the key technique of automatic alignment, according to the image relay of the pinhole, utilizing the optical position and the spatial location of the four pinholes of the main spatial filter in the four-pass beam in the SG-Ⅲ, this paper presents a reasonable scheme for automatic aligning in the four-pass amplifier, which has been fully checked on the multi-pass amplifier experiment system．The centering sensitivities of the system are less than 0.5% of the beam diameter. The pointing sensitivities of the system are less than 10μm.
2004,
16.
Abstract:
This paper presents the preparation of patially brominated poly-4-methyl-1-pentene(PMP).The composition and stucture of patially brominated PMP are studied by means of element analysis，IR and TGA. Br atom was found to be substituated easily with H atom of PMP to form the chemical doped polymers．The polymer will be stabilized below 150℃and lose the HBr up to 150℃. The well doped low density material was made by this means.
This paper presents the preparation of patially brominated poly-4-methyl-1-pentene(PMP).The composition and stucture of patially brominated PMP are studied by means of element analysis，IR and TGA. Br atom was found to be substituated easily with H atom of PMP to form the chemical doped polymers．The polymer will be stabilized below 150℃and lose the HBr up to 150℃. The well doped low density material was made by this means.
2004,
16.
Abstract:
The experiment measured the fine spectrum structure of 2 doubling harmonic at near normal direction of target and reflection direction of laser wave, employing OMA optical multi-channel spectrometer. Under the intensity of 5×1017W/cm2, the result of measurement indicates that spontaneous magnetic field was up to 102T level by analyzing the fine structure of 2 doubling harmonics in laser-plasma interaction.
The experiment measured the fine spectrum structure of 2 doubling harmonic at near normal direction of target and reflection direction of laser wave, employing OMA optical multi-channel spectrometer. Under the intensity of 5×1017W/cm2, the result of measurement indicates that spontaneous magnetic field was up to 102T level by analyzing the fine structure of 2 doubling harmonics in laser-plasma interaction.
2004,
16.
Abstract:
It is important to calculate the temperature change and heat flux in the surface of the limiter in HT-7 for analyzing the influence of its function on the plasma during long pulse discharge. In this paper, the heating flux density was calculated by the curve of temperature at 3mm from limiter surface. for many long pulse shots, temperature at a few local points was over 1 000℃, and deposited power flux density exceeded 10MW/m2. But by effectively controlling plasma position, temperature dispersal was more uniform and plasma discharge was easily sustained. The influence of limiter materials and construction on the temperature change of limiter surface was discussed; in-time cooling power of water was analyzed.
It is important to calculate the temperature change and heat flux in the surface of the limiter in HT-7 for analyzing the influence of its function on the plasma during long pulse discharge. In this paper, the heating flux density was calculated by the curve of temperature at 3mm from limiter surface. for many long pulse shots, temperature at a few local points was over 1 000℃, and deposited power flux density exceeded 10MW/m2. But by effectively controlling plasma position, temperature dispersal was more uniform and plasma discharge was easily sustained. The influence of limiter materials and construction on the temperature change of limiter surface was discussed; in-time cooling power of water was analyzed.
2004,
16.
Abstract:
A high power LD pumped acousto-optic Q-switched Nd:YVO4 laser is reported. Short pulse of 1 064nmis obtained. Output energy, pulse width and average output power are measured with different conditions such as different output coupling mirrors and repetition rates. When repetition pulse is 50kHz, the maximum average output power of 5.72W is obtained with an optical conversion efficiency of 28% and a slope efficiency of 32.4%.As repetition is 10kHz and pulse width is 22ns, the maximum single pulse energy of 0.286mJ and peak power of 13kW are acquired.
A high power LD pumped acousto-optic Q-switched Nd:YVO4 laser is reported. Short pulse of 1 064nmis obtained. Output energy, pulse width and average output power are measured with different conditions such as different output coupling mirrors and repetition rates. When repetition pulse is 50kHz, the maximum average output power of 5.72W is obtained with an optical conversion efficiency of 28% and a slope efficiency of 32.4%.As repetition is 10kHz and pulse width is 22ns, the maximum single pulse energy of 0.286mJ and peak power of 13kW are acquired.
2004,
16.
Abstract:
This paper analyzes the mechanism that ignitron prefires when it is used in new discharge circuit of power conditioning system for high power laser. The performance of ignitron is improved with a coaxial structure. The coaxial structure not only controls discharge current flowing through the center of ignitron but also shields the electric field produced by the ignitron. The ignitrons have successfully run over 2 000 shots in 4×2×3 amplifier system without prefire.
This paper analyzes the mechanism that ignitron prefires when it is used in new discharge circuit of power conditioning system for high power laser. The performance of ignitron is improved with a coaxial structure. The coaxial structure not only controls discharge current flowing through the center of ignitron but also shields the electric field produced by the ignitron. The ignitrons have successfully run over 2 000 shots in 4×2×3 amplifier system without prefire.
2004,
16.
Abstract:
Automated antenna design has already become the latest trend of antenna design. An approach, which is based on the genetic algorithm (GA) and the NEC2 (numerical electromagnetics code, version 2) in conjunction with the parallel computation technique, is explored in this paper to design and optimize helical antennas. Three kinds of antennas have been optimized by the approach: a uniform helical antenna with a gain of 12.68dB, which is 3.38dB higher than that created by traditional design methods; a tapered helical antenna with average gain 12.28dB in frequency band 400~800MHz; and a tapered helix-conical horn antenna. Results show the approach is more efficient than traditional design methods and can solve different antema design problems of widely varying complexity, including those too d
Automated antenna design has already become the latest trend of antenna design. An approach, which is based on the genetic algorithm (GA) and the NEC2 (numerical electromagnetics code, version 2) in conjunction with the parallel computation technique, is explored in this paper to design and optimize helical antennas. Three kinds of antennas have been optimized by the approach: a uniform helical antenna with a gain of 12.68dB, which is 3.38dB higher than that created by traditional design methods; a tapered helical antenna with average gain 12.28dB in frequency band 400~800MHz; and a tapered helix-conical horn antenna. Results show the approach is more efficient than traditional design methods and can solve different antema design problems of widely varying complexity, including those too d
2004,
16.
Abstract:
Using the software high frequency structure simulator(HFSS) and Maxwell's equation by the finite integration algorithm(MAFIA), a disk-loaded waveguide of relativity traveling wave tube is simulated to get the dispersion characteristics. Based on this work, a broadband and a narrowband disk-loaded waveguide for the relativity traveling wave tube are designed. The “cold test” of the two waveguides is fulfilled, and the simulation results accord with measured values very well. It proves that both electromagnetic codes are capable of simulating eigenvalue problems of slow-wave structures of traveling wave tube.
Using the software high frequency structure simulator(HFSS) and Maxwell's equation by the finite integration algorithm(MAFIA), a disk-loaded waveguide of relativity traveling wave tube is simulated to get the dispersion characteristics. Based on this work, a broadband and a narrowband disk-loaded waveguide for the relativity traveling wave tube are designed. The “cold test” of the two waveguides is fulfilled, and the simulation results accord with measured values very well. It proves that both electromagnetic codes are capable of simulating eigenvalue problems of slow-wave structures of traveling wave tube.
2004,
16.
Abstract:
The exposure of a system to an X-ray or γ-ray environment produces system generate electromagnetic pulse (SGEMP). The X-ray or γ-ray generate emissions of photoelectrons, Compton electrons and secondary electrons from surface of system materials, which produce photo Compton currents in the space within and about the system structure. These photo-Compton currents generate electric and magnetic fields which couple energy into the system electric circuit. For most SGEMP interest is the net number of electrons crossing a boundary at the interface between dissimilar material. In the paper the responses to SGEMP of aerocraft while it is exposed in the pulse X-ray radiation environment induced by high altitude nuclear explosion are analyzed. The mechanism, magnitude and couple approach to syste
The exposure of a system to an X-ray or γ-ray environment produces system generate electromagnetic pulse (SGEMP). The X-ray or γ-ray generate emissions of photoelectrons, Compton electrons and secondary electrons from surface of system materials, which produce photo Compton currents in the space within and about the system structure. These photo-Compton currents generate electric and magnetic fields which couple energy into the system electric circuit. For most SGEMP interest is the net number of electrons crossing a boundary at the interface between dissimilar material. In the paper the responses to SGEMP of aerocraft while it is exposed in the pulse X-ray radiation environment induced by high altitude nuclear explosion are analyzed. The mechanism, magnitude and couple approach to syste
2004,
16.
Abstract:
This paper presents a novel antenna of NEMP (nuclear electromagnetic pulse) radiating-wave simulator, which is analyzed and optimized using the finite-difference time domain (FDTD) method. The intense voltage pulse is fed as the source to this antenna by the coaxial line. The parallel plate transmission line and the size of the transverse electromagnetic horn are optimized. The near field of antenna is analyzed, and the effects of the size on the near field are also given. The antenna designed in this paper can well satisfy the requirement for studying the EMP effects．
This paper presents a novel antenna of NEMP (nuclear electromagnetic pulse) radiating-wave simulator, which is analyzed and optimized using the finite-difference time domain (FDTD) method. The intense voltage pulse is fed as the source to this antenna by the coaxial line. The parallel plate transmission line and the size of the transverse electromagnetic horn are optimized. The near field of antenna is analyzed, and the effects of the size on the near field are also given. The antenna designed in this paper can well satisfy the requirement for studying the EMP effects．
2004,
16.
Abstract:
In this paper, a new high power and wideband amplifier with permanent periodic magnet(PPM) focusing is presented. It consists of klystron and FEM . Focusing, bunching and emiting of the electron beam in this device are studied theoretically. The radiation parameters of the device have been estimated as the frequency is 11.4GHz, output power 18MW and output bandwidth rate 44% at the conditions in which a order of modulating coefficiency is 30% of the klystron, radius of the waveguide 1.51cm, the amplitude 0.16T and period 7.92cm of the magnetic field of the wiggler, and the voltage is 490kV, current 50A and radius 0.368cm of the electron beam.
In this paper, a new high power and wideband amplifier with permanent periodic magnet(PPM) focusing is presented. It consists of klystron and FEM . Focusing, bunching and emiting of the electron beam in this device are studied theoretically. The radiation parameters of the device have been estimated as the frequency is 11.4GHz, output power 18MW and output bandwidth rate 44% at the conditions in which a order of modulating coefficiency is 30% of the klystron, radius of the waveguide 1.51cm, the amplitude 0.16T and period 7.92cm of the magnetic field of the wiggler, and the voltage is 490kV, current 50A and radius 0.368cm of the electron beam.
